We have one of those "cat scarers" in the garden that work by emitting a high pitched sound when there is a movement within the range of the device. In theory I believe the frequency that is emitted is uncomfortable specifically to cats only. But we noticed that since the start of the year we have not seen either foxes or hedgehogs in our garden, whereas last year we observed both animals. On several occasions we saw a fox and a hedgehog feeding together from the same bowl! And in the Spring of 2014 we had as many as 4 hedgehogs feeding on the patio at night time.

When we saw a pile of feathers earlier this year and two or three cats skulking under shrubs and a hedge I realised that I needed to replace the battery in the cat scarer to protect the many varieties of birds visiting. However, since the high pitched frequency has not been operating we have seen both fox and hedgehog again, for 3 days in a row! So I'm wondering whether the cat scarer has been scaring both foxes and hedgehogs as well as cats? Do I replace the battery to protect the birds or forget it and allow the hedgehogs and fox to return?